As I’ve been discussing the biomedical research workforce with people in the extramural community over the past few months, I’ve heard people say things like “PhDs don’t do much research with human subjects”. I decided to look into data that could support or refute statements such as this, and started with checking data on the use of animal and human subjects in research.

As you can see in the graphs below, we looked at awards by degree over the past 10 years and grouped them into four categories based on the research described in the grant applications: 1) human subjects research only (defined as having been reviewed by an Institutional Review Board), 2) animal subjects research only (defined as having been reviewed and approved by an Institutional Animal Care and Use Committee), 3) no human or animal subjects, or 4) both human and animal subjects.

To put these data in context, you’ll remember that about 70% of NIH-funded PIs have PhDs, with most of the remaining PIs having either an MD or an MD/PhD. Since the number of PIs with other degrees (DDS or DVM only, for instance) is very small, we’ve provided those data separately – see the footnote below.

First, we took a look at human and animal subject use by each degree category: PhDs, MD/PhDs, and MD.  As shown in figure 1, among PIs with a PhD degree, about 45% of PhDs engage in research involving only animal subjects, about 22% engage in human subjects research, a little less than 30% do research with no human or animal subjects, and only 5% conduct research with both. These proportions haven’t changed much over time.  

The breakdown for PIs with MD/PhD degrees is slightly different (figure 2).  A higher proportion – over 50% – engage in research with animal subjects only, nearly 22% conduct research involving human subjects only, while around 10% do research with no human or animal subjects and another 10% with both.

Looking at PIs with MD degrees, we see MDs are likely to engage in research solely involving human subjects (approximately 45%), and also likely to engage in research involving only animal subjects (nearly 35%). However, they are the  least likely to conduct research that involves no human or animal subjects – only about 8% of MDs conduct research that does not involve human or animal subjects (figure 3).

In this last graph we’ve pulled out the human subjects only percentages for each of these 3 degree categories and compared them all on one graph. As shown in figure 4, investigators with MD degrees do tend to work on research involving only human subjects. This is not too surprising, though it is interesting that such a significant and similar percentage of PIs with a PhD and MD/PhD do research exclusively with human subjects.

Taken together, these data support the idea that many PIs are conducting research that fits with their academic training, but a substantial number of PhD-trained scientists are doing research with human subjects and many clinician-scientists (either MDs or MD/PhDs) conduct research with neither human nor animal subjects.  Also, changes in the extramural community over the past decade do not seem to have affected these proportions significantly.  These data may prove useful to the new advisory committee to the director’s working group on clinician-scientists.

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Note: The data table corresponding to these figures is posted on RePORT and can be downloaded in an Excel file. The table includes data for other advanced degrees (e.g. DVM, DDS, and DMD), which were not plotted on the charts because of their small numbers.

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